1. Field of the Invention
This invention relates to electromagnetic precision positioners operable to provide precision positioning capability to a robot end effector, and more particularly relates to an electromagnetically powered X-Y-Theta positioner device, comprising an armature platform supported for X-Y-Theta motion by a spring colonnade basket in juxtaposition to its stator, which positions operates without static friction, with controlled power and compliance with precise control of position, and with positional feedback for closed loop servo operation.
2. Description of Related Art
The need for precision positioning is well known in a number of mechanical and electronic arts. Close tolerance machining, for example, requires that the tool be positioned exactly. Various mechanisms for accomplishing such positioning, and various techniques for getting the most out of such mechanisms, are known.
A known mechanism for accomplishing precision positioning within a plane is the use of a linear motor to drive and hold a device in a particular position. Such linear motors, as well as electromechanical stepping motors, hydraulic actuators, and other mechanisms are known for use in precision positioning.
A typical solution to the need for high precision motion, in a plane of scanning for a robot end effector, is to provide a pair of linear actuators mechanically connected in tandem so that the Y-actuator is physically carried at the end of the X-actuator. A disadvantage of this approach is that the Y and X stages are mechanically in series, the Y stage moves the payload, but the X stage must move both the Y stage and the payload. Symmetry is broken, and in critical applications the control strategies for the X stage and the Y stage must be different for the different dynamics involved. Theta motion (rotation about an axis orthogonal to X and Y) may require still another tandem stage.